Lentiviruses constitute a class of viruses which can lead to a variety of diseases in both humans and animals. These diseases are often preceded by several months or even years of incubation. For example, the pathologies associated with AIDS are caused by the human immunodeficiency viruses (HIVs) and result from a chronic progression of the disease, often times causing cachexia and death in the patient several years after infection.
Lentiviruses have also been associated with various pathologies in such species as apes and monkeys, as well as domesticated animals such as horses, burros, cattle, goats, and sheep. Among these, equine infectious anemia (EIA) has been characterized as the most important infectious disease of horses occurring throughout the world. Lentiviruses of sheep are relatively common pathogens in most parts of the world, and include Maedi-visna virus and progressive pneumonia virus as two predominate types. Bovine immunodeficiency virus is an important cause of illness in cattle.
Other lentiviruses are vital indicators of pathology in animals such as cats. Feline immunodeficiency virus, structurally similar to HIV, can cause death in house cats. Increasingly, doctors, veterinarians, and researchers are devoting considerable time and resources to preventing and treating diseases caused by these viruses.
Part of the research involves growing tissue cultures containing cells, for example lymphocytes, which have been infected with one or more of the known lentiviruses. Lymphocyte cultures or anchorage dependent epithelium-like cells such as feline kidney cell cultures may be grown in T-flasks, roller bottles, spinner flasks and bioreactors using media such as Minimal Essential Media (MEM), Roswell Park Memorial Institute (RPMI), Dulbecco's MEM (DMEM), and AIM V (Gibco/LTI, Grand Island, N.Y.) supplemented with bovine serum up to about 20% and up to about 5% bovine serum albumin (BSA). Large-scale cultures may be grown in large spinners, fermentor, and bioreactors in the presence of shear protective chemical, thickener, emulsifiers or compounds such as methylcellulose, carboxylmethyl cellulose, and surfactants such as the Pluronic series, e.g. PLURONIC® F-68, manufactured by BASF Corporation of Wyandotte, Mich.
In maintaining tissue cultures containing viruses, researchers seek to destroy harmful bacteria within the culture so that the cells containing the virus can grow and propagate. At the same time, a concomitant goal is to maximize growth of the cell culture. To facilitate growth and destroy bacteria, it has been accepted practice to add antibiotics, usually a combination thereof, to the cell culture. For example, U.S. Pat. No. 5,958,423 sets forth a cell culture of Madin-Darby Bovine Kidney (MDBK) cells in which up to 30 mcg/mL of polymixin B and neomycin, and up to 2.5 mcg/mL of amphotericin B is utilized.
What is now needed in the art are new cell culture compositions containing cells infected with lentiviruses. Especially needed are novel cell cultures in which cell growth can be maximized and the presence of harmful organisms such as bacteria can be simultaneously minimized. Also needed are new methods of growing cell cultures in which the density thereof can be increased through the promotion of tissue growth. Further needed are new additives which can optimize the density of cell cultures by enabling and enhancing the growth of the cells which comprise the culture.